The notion of adoptive cellular immunity was first conceived and reported by A.V. Mitchison1 more than 60 years ago. Since then extraordinary human effort and ingenuity has resulted in fundamental understandings of molecular biology, the immune system, genetics, gene therapy and the dreaded disease cancer. That has enabled the creation of incredible tools - inconceivable a generation ago - which has put medical science on the threshold of cancer cures. One part of that 'tool box' is the isolation of subsets o immune cells from patients/donors and the purification of genetically modified cells. Currently, CD3+ cells are the prime targets of such separations. Cost effective/efficient separations are vitally important given the expense such treatments entail. The goal of this proposal is to test the feasibility of a clinical scale immuno-magnetic cell separation system that has the potential to be faster (3-fold), cheaper (2-fold) and better (yield & purity) for the isolation of CD3 + cell than the system of Miltenyi Biotec and other improvised systems in use at many centers. This proposal is based on extraordinary benefits our magnetic nanoparticles confer to cell separations. These ferrofluids are crystalline quasi-spherical 120 nm cores of magnetite crystals coated with modified protein to which common capture agents (streptavidin, antibodies) or Mabs (direct conjugates) are coupled. They are stable, have been in commercial use more than 10 years and are the key component of the FDA-approved CellSearch(r) circulating tumor cell enrichment scheme. Benefits: (a) rapid binding kinetics as they diffuse (b) extraordinary surface area; thus, low mass input for targeting (c) most magnetic superparamagnetic materials in existence (greater than 95% magnetite - most magnetic superparamagnetic material) (d) easy to GMP manufacture and filter sterilize (e) separable from open vessels (test tubes, flow through chambers/closed containers vs. Miltenyi's that require ultra-high gradient magnetic forces, ball bearing packed, expensive and inefficient columns. With in-house designed magnetic devices, ferrofluids can collect cells in monolayers or multilayers that are easily retrievable. Unlike larg Dynal Dynabeads, ferrofluids do not damage cells, clutter up cell surfaces nor affect cell viability. This work benefits from 3 years of extensive R&D in improving our ferrofluids' magnetics and surface chemistries resulting in use of less material, significantly lower non-specific binding and improved purity as well as more latitude in collection chamber design because of their magnetics. From fundamental discoveries on cell separation, that use very little Mab, it is feasible to target 30% of a 1010 cell starting product with 30 ug of Mab (vs 1000 ug for competing systems) and with only 4 mg of 5th generation ferrofluid. And the entire separation can be done in less than 30 minutes. Our skill set/ experience: PI founded/managed Immunicon Corp., conceived of CellSearch(r), designed seminal experiments showing that tumor cells circulate early on in cancers, recruited the development team for commercial and FDA approved system and started the corporate partnership with Johnson & Johnson. All of that began with a Phase I SBIR. 1 . A.V. Mitchison, J Exp Med. 1955 Aug 1; 102(2): 157-177. [The PI was fortunate to have had the benefit of close contact and interactions with Av Mitchison (University College, London) while the PI was a Visiting Scientist at NIMR, Mill Hill working in the laboratory of the late Bridgette Askonas. We had many discussions on how to use the immune system to attack malignancies.]